Electric vehicles that use electricity as a power source have come into practical use in recent years from the viewpoint of reducing carbon dioxide emission and increasing energy use efficiency. Following this, infrastructure for charging electric vehicles is beginning to be set up in various places. It takes a considerable amount of power, in the order of a dozen or so kilowatt-hours, to fully charge the battery of an electric vehicle (2-3 days worth of power when converted to the average electric power consumption of an ordinary household). Thus, the task is to enhance the functions of power supply facilities (grid) for electric vehicles, such as load adjustment and power distribution control.
In view of this, technology called Vehicle-to-Grid (V2G) or Vehicle-to-Home (V2H) has been proposed, in which power supply infrastructure such as power plants is connected through communication to electric vehicles, and the power supply facility performs battery charge processing that is most suitable to the amount of electric power that can be supplied from the power supply facility, and bills and settles payments in accordance with the amount of electric power used to charge the electric vehicle. For example, Patent Document 1 below proposes a power supply system in which power line communication (hereinafter, referred to as “PLC communication”) using a charging cable of an on-board battery is used to notify power supply infrastructure of user information that indicates the user to be billed for battery charging, and to bill the user according to the amount of electric power charged.
In recent years, a next-generation electric power network called a “smart grid” that incorporates an auto-controller for controlling supply and demand of electric power has also been attracting attention. An electric power network managed by a smart grid focuses not only on charging the on-board battery (supplying power from the grid to the vehicle) but also actively discharging the on-board battery (supplying power from the vehicle to the grid).